Spatially　non-uniform　electrical　performance　in　ZnO　varistor　ceramics,　which　restricts　application　for　higher　energy　absorption　capability,　is　investigated　in　terms　of　electronic　relaxations　corresponding　to　intrinsic　point　defects.　Decreased　breakdown　field　and　nonlinear　coefficient　are　observed　from　135.5　V/mm　and　53　in　central　area　to　122.0　V/mm　and　20　in　peripheral　area　as　well　as　significantly　increased　leakage　current　density　from　3.4　μA/cm2　to　18.3　μA/cm2.　From　microstructure　analysis,　grain　size　distribution　is　found　relatively　homogeneous,　suggesting　that　electrically　non-uniform　grain　boundaries　should　be　responsible　for　divergent　electrical　properties.　Investigation　via　energy　dispersive　spectrometer　(EDS)　shows　higher　Zn/O　ratio　in　peripheral　area,　indicating　higher　possibility　of　generating　intrinsic　point　defects　like　zinc　interstitials　and　oxygen　vacancies.　This　is　further　verified　via　dielectric　spectroscopy　that　the　densities　of　zinc　interstitials　and　oxygen　vacancies　are　both　larger　in　peripheral　area　than　those　in　central　area.　Oxygen　is　easier　to　be　removed　from　ZnO　lattice　and　diffuse　into　atmosphere　during　high-temperature　sintering　process,　resulting　in　larger　amount　of　oxygen　vacancies　in　peripheral　area.　Meanwhile,　more　zinc　atoms　are　removed　from　lattice　and　form　interstitials　as　a　result　of　distortion　of　ZnO　lattice　in　peripheral　area.　Increased　donor　density　in　peripheral　area　attributed　by　oxygen　vacancies　and　zinc　interstitials　results　in　decreased　Schottky　barrier　height.　Non-uniform　distribution　of　Schottky　barrier　height　is　the　origin　of　overall　electrical　inhomogeneity.　©　2018　Elsevier　Ltd　and　Techna　Group　S.r.l.